Salamanders hit the treadmill in the name of science

We've all heard stories of hopeless romantics chasing would-be partners across great distances, and as it turns out, a similar allure applies in the world of salamanders. A new study, in which these adventurous amphibians were put to work on the treadmill, has found that they sometimes travel up to nine miles (14.5 km) to find a mate, teaching scientists concerned with their conservation more about how they procreate.

When it comes time to mate, the majority of salamanders will partner up with another salamander close to home. But some choose to cast their eye further afield. Much, much further afield, according to a team of Ohio State University researchers.

The scientists set out to fill in some of the blanks surrounding the traveling habits of mating salamanders, with a view to informing approaches to their conservation. This meant gathering DNA samples from 445 salamanders living in various wetlands across Ohio, and then cross referencing this information with how far the animals are able to travel before tiring out.

Observing the animals in the wild might be one way of getting some answers to this question, but salamanders are pretty adept at staying hidden and can't be tagged with tracking devices due to their fragile skin, so the researchers opted for another approach.

They built a miniature treadmill with plastic walls and placed salamanders inside, giving them a little poke in the butt or pinch of the tail to get them moving. Two types of mole salamanders were put to the test, one all-female kind that reproduces by cloning or collecting sperm left behind by males, and another type that mates in the traditional way.

The so-called sexual salamanders (the traditionalists) were able to walk on the treadmill for an average of four times longer than the all-female salamanders before becoming fatigued. Fatigue was measured as the point when the salamander took more than a few second to correct its body position after being placed onto its back.

"They're like endurance athletes," said lead author Robert Denton. "Some of them could walk for two-plus hours straight without tiring themselves. That's like a person lightly jogging for 75 miles (120 km) before wearing out."

The information gathered through the treadmill tests paired up with that gathered in the wetlands, with the sexual salamanders found around twice the distance from their birthplace as the all-female salamanders. The researchers say that when the wandering salamanders leave home for another salamander outpost, they travel an average of six and up to nine miles (9.6 and 14.5 km).

"Maybe the best explanation for why sexual salamanders travel so far is because they have to," said Denton. "On a large landscape with few places to breed, the animals that can cross that distance are the ones that survive and reproduce. Perhaps the more interesting question is why the all-female salamanders don't go very far, and we think that has to do with the physiological costs of not having sex. Essentially, not mixing up your genomic material often enough likely causes some problems for genes that you need to make energy."

The research was published in the journal Functional Ecology, while you can see the salamanders go to work on the treadmill in the video below.